﻿10 L. Scliwendler — On the general Theory of Dii^plex Telegraphy. [No. 1, 



signalling speed. (The forces in this case are proportioned to the true 

 currents.) The latter problem being far the more intricate and for my 

 special purpose only of secondary importance, I shall begin with the solution 

 of the first. 



Solution op the 1st Peoblem eoe kwz giyei!^ Duplex Method. 



What is the best arrangement of any given duplex method, when the 

 line is regarded as a variahle conductor, hut not as acting perceptibly as a 

 Ley den jar ? 



I. The Bridge Method.* 



This arrangement for duplex working is based on the well known 

 method of comparing electrical resistances " Wheatstone's Bridge," and 

 Figure 1 gives the general diagram, when this method is applied for duplex 

 working. 



mgi. 



It has also been proposed to use Ruhmkorflf's coils for balancing tbe effect of charge and 

 discharge. This method, however, I believe must be always much inferior to the one 

 of using condensers, inasmuch as the strength of a Voltaic induction current scarcely 

 depends on the speed of signalling. Mobile the charge and discharge of a line, it is well 

 known, is not at all an inconsiderable function of the signalling speed. 



Therefore, if the strength of the induction current had been adjusted to balance the 

 charge and discharge of the line for a certain signalling speed, the balance would be consi- 

 derably and at once distm*bed if the speed varied even slightly ; and since so long as 

 hand signalling is used a certain variation in the speed of signalling will always exist, 

 this method will prove a failure, or at all events will render fresh adjustments more fre- 

 quently necessary than when condensers are used. 



* Dr. Wr. Siemens mentions this method in Pogg. Aim. Vol 08, p. 122, 1856. 



